Modern cellular telecommunication systems and terminals of such systems are capable of supporting device-to-device communication capabilities for efficient and cost-effective content delivery, network operation and performance. Accordingly, two terminals located relatively close to each other in the same cell may be configured by the network to communicate over a direct connection instead of routing the data through a cellular network. It is even known that an ad hoc network among multiple terminal devices may be formed based on the IEEE 802.11 standard, for example, and connections with the cellular network may utilize this ad hoc network to improve the overall coverage and performance of the cellular system. This is implemented by providing a shadowed terminal device with a relayed connection to a serving base station through a relay terminal. The relayed link utilizes a device-to-device connection between the shadowed terminal device and the relay terminal and a regular cellular connection between the relay terminal and the serving base station. As a consequence, the relayed terminal effectively relays data of the shadowed terminal device.
Control signaling related to such relayed communication links is challenging in terms of compatibility with the cellular system, simplicity and protocol overhead.